1. Field of the Invention
The present invention relates to a method for cleaning a thermal head, relative to an opposed platen, which prints a character on a sheet fed into a gap between the head and the platen.
2. Description of the Related Art
A label printer as shown, for example, in FIG. 1 is known as an apparatus using a thermal head. A supply roll 1 on which a "label" web is wound is provided on an external location of a body. The label web 2 is fed from the supply roll 1 and past a guide 3 into a gap between a platen 4 and a thermal head 5. An ink ribbon supply roll 6 is provided in the apparatus. An ink ribbon 7 is fed from the roll 6 past guide rolls 8 and 9 into the gap between the platen 4 and the thermal head 5 and from there past a guide roll 10 to a take-up roll 11 where it is wound.
The thermal head 5 is brought into proximity to the platen side with the web 2 and ink ribbon 7 sandwiched therebetween and comes into contact with the ink ribbon 7 to print a character on the web 2.
In order to increase an intimate contact between the web 2 and the thermal head 5, the thermal head 5 as shown in FIG. 2 has a somewhat raised printing surface portion in its width direction at an area where a heat generating element 5a is buried. During a prolonged use of the thermal head 5, an ink deposit, paper dust and so on are attached to the side surface of the raised surface portion of the thermal head, posing problems upon printing, such as blurred character impression or soiled paper.
For this reason, the thermal head is swingably mounted relative to the body and, upon the occurrence of an inconvenience, or its likelihood, upon printing, it is swung away from the body so that the printing surface of the head may be cleaned (Japanese Patent Disclosure (KOKAI) 58-36479).
In order to allow the thermal head to be swung relative to the body, extra members are necessary and a corresponding arrangement becomes complicated due to the swinging motion of the thermal head and the maintenance of that motion. Further, if their mounting operation is not exactly done, the inconveniences are produced upon printing.
For this reason, with the thermal head mounted relative to the body, a deposit on the near-forward end portion of the thermal head 5 is manually rubbed out by a pen type cleaning unit 12 with a silicone impregnated at the tip of a felt as shown in FIG. 3.
Even if the pen type cleaning unit 12 is used, the tip end of the unit 12 may be accessed to a narrower clearance between the platen 4 and the thermal head, but an adequate cleaning cannot be effected over the whole surface of a printing area. A cumbersome operation is, therefore, necessary.